Young people and cannabinoids: current research and implications for tobacco control

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Transcript of Young people and cannabinoids: current research and implications for tobacco control

Professor Harry Sumnall Centre for Public Health, LJMUYoung people and cannabinoids: current research and implications for tobacco control"The best evidence based advice to help cannabis smokers look after their lungs would be to abandon the peculiar British habit of mixing cannabis with tobacco” (Prof D. Nutt, June 2012)Alternatives to smoking?Small case studies & cross sectional surveysTobacco use decreased - refused to return to smoking; Self-reported respiratory symptoms significantly improved.Measures of lung function (forced expiratory volume (FEV1) and forced vital capacity (FVC)) improved. Need for a larger clinical trialVapourisers can create THC blood levels that are comparable to smoking, but unlike smoke, the vapour contains little other than cannabinoidsVapourisersGood quality vapourisers are expensive (£100+)Not very practical for many usersUK cannabis culture of smoking jointsUnder Section 9A of the Misuse of Drugs Act 1971, it is a criminal offence to supply or offer to supply articles for administering or preparing controlled drugs.About meProfessor of Substance Use, CPH, LJMUPresident, EUSPRMember, ACMDConduct funded research into prevention, evidence based practice/policy, psychopharmacologyWhat links tobacco and cannabis use?Strong epidemiological evidence to show co-use of cannabis and tobaccoMost common form of polydrug use (involving an illegal substance) In the UK cannabis historically smoked with tobacco - availability, price, smoking behaviour (vs USA)Joints produce greater increases in plasma THC and subjective ratings of intoxication, strength, and quality compared to pure cannabis joints ('blunts').Cannabis use is associated with initiation of tobacco in teensSmoked tobacco use is a predictor of cannabis use, especially in young adulthoode.g. in one Australian study, weekly teen use of cannabis predicted a more than eightfold increase in the odds of later initiation of tobacco useFor 21-year-old smokers, not yet nicotine-dependent, daily cannabis use raised the odds of nicotine dependence at the age of 24 years more than threefoldLooking at other factors, cannabis use seems second only to previous tobacco use as a predictor of tobacco dependence.Reverse 'gateway'?Why?Shared route of administration - 'learning to smoke'Tobacco in joints? Effect still significant after controlling for peer use of tobacco Not a motivational effect, previous cannabis use not always associated with reduced tobacco quit attempts/successCommon actions on brain reward systems?Substitution effect, e.g. at school, workAlleviation of cannabis withdrawal?UK cannabis joint smokers are therefore tobacco users. In effect, are many of the risks of cannabis use the same as that of tobacco?Do cannabis joint smokers self-identify as being tobacco smokers? Implications for preventionVery few studies have specifically investigated prevention of co-use of tobacco and cannabisMore studies have investigated prevention of cannabis (which would also include co-use)Most studies are in school aged children, fewer in older young people, and adultsMajority from the USAPrevention approachesUS Iowa Strengthening Families Program, slowed the growth of polysubstance use (including tobacco and cannabis) from 6th through 12th gradesEnforcement of smoke free US University halls of residence policies led to reduced cannabis use Brief 1 to 1 consultation about health promotion led to reduced use frequency at + 12 monthsUK BI in FE colleges showed short (+3m) but not long (+12m) term effects on tobacco and cannabis use(Swiss)YP views vs tobacco"Cannabis is more natural""Cannabis is more healthy""Cannabis is more ethical""Tobacco has no purpose""Easier to quit joints than tobacco"Cannabinoid receptor agonists ('synthetic cannabis')

Potentially hundreds available, only a small number controlled under the Misuse of Drugs Act 1971Cannabis-like effect: mild euphoria, relaxation, introspection, perceptual changesMany have a greater potency at CB1/CB2 R than ‘natural’ THC (full vs partial agonist activity)Effects of herbal cannabis on memory problems, psychopathology and psychosis proneness dependent on THC:CBD ratioCBD is an indirect antagonist of THC, thus moderating some of the adverse psychological effects of cannabis. Smoking mixtures lack the moderating effect of CBDLong term effects unknownSchool based preventionSchool based cannabis prevention activities *can* have an impact upon use:Meta analysis of 15 studies (n=15,571 students) produced a moderate effect size of 0.58Social learning/influence approaches had less of an effect than other typesLength of programme important (e.g. >15 sessions)Delivery by non-teachers more effectiveDelivery to older students has greater effect

(Porath Waller et al., 2010)UK Youth attitudes (from Eurobarometer 2011):59% want cannabis to remain banned; 34% regulated; 5% available without restriction15% want tobacco to be banned; 65% regulated, 19% available without restriction57% favour 'tough measures against dealers'36% favour reduction of poverty and unemployment as the best way to reduce drug problemsMental health risksControversialLongitudinal studies from Sweden, Israel, ND, NZ suggest that risk of developing psychotic symptomatology or being hospitalised with schizophrenic disorder is approximately doubled in cannabis usersBrief psychotic episodes, exacerbation and return of symptoms, poor medication response etc. also importantHowever:Risk still lowModelling by Hickman and colleagues ('09/'10) suggests that you would need to prevent between 3000-5000 heavy, and 10-30,000 light users from smoking to prevent a single case of schizophreniaConsidering small effects of intervention, uncertain cost-effectiveness, lack of availability and investment, prevention of mental health problems in general pop. shouldn't be focus of interventionsSummaryCannabis prevention should be considered an important component of tobacco prevention effortsFor many UK users, health harms of cannabis are the same as tobaccoPreventing lifetime use probably less important than progression into heavy patterns of useCan we persuade users to remove tobacco from their polydrug repertoires?How can we work within existing laws and regulations?Prevention can work!Information provision alone does not change cannabis use behaviourBecause cannabis is illegal we have fewer 'tools' available to us to reduce use/harmsFewer controls over 'marketing'*Mostly * privately smoked, hence few environmental interventionsFew opportunities for supportive community based interventionsFew opportunities for 'self-help'No useful 'THC replacement therapy', although Sativex being trialled in AustraliaJune 2012 BLF report :"Risk of developing lung cancer is up to twenty times greater in a cannabis cigarette than in a tobacco cigarette – yet 88% of the public believe tobacco cigarettes pose the greater risk""A third of people believe cannabis does not harm your health - despite established scientific links to TB, acute bronchitis, lung cancer and other health problems"However:No critical appraisal of cited studies - small, 'underpowered' studiesConflicting evidence on lung cancer, some studies show no effect, or even protective effect. Use patterns important - effects only seen in long term smokers (10+ years); linear effects incorrectly assumedCo-use of tobacco v.importantcontact:h.sumnall@ljmu.ac.uk@profhrs36% classed as 'frequent users'